use tokio::sync::OnceCell;
static ONCE: OnceCell<u32> = OnceCell::const_new();
async fn get_global_integer() -> &'static u32 {
    ONCE.get_or_init(|| async {
        1 + 1
    }).await
}
#[tokio::main]
async fn main() {
    let result = get_global_integer().await;
    assert_eq!(*result, 2);
}